You have been researching protein kinase A (PKA) and believe there may be a link between PKA and learning. In some cells, PKA works via a signal transduction pathway (see image). It is also known that activated PKA phosphorylates the transcriptional regulator called Drizzy that then activates transcription of the gene AubGr.

Which situation will lead to an increase in AubGr transcription?

- The addition of an endoplasmic reticulum signal sequence to the N-terminus of PKA

- An adenylyl cyclase mutation that decreases its binding to ATP

- A regular intake of caffeine, known to inhibit cAMP phosphodiesterase

- A mutation in Drizzy that removes the amino acids normally phosphorylated by PKA